Medical procedures for treating a variety of neurological conditions, for example, Parkinson's disease, essential tremor and dystonia, require access to the brain, typically through a burr hole formed in the skull, for the insertion of deep brain stimulating electrodes. Burr holes may also be formed for the insertion of a delivery catheter, for example, to provide drug therapy for similar conditions. Stereotactic apparatus and procedures, which are known to those skilled in the art, may be employed by surgeons to locate inserted electrodes and/or drug delivery ports in target regions of the brain.
FIG. 1A is a perspective view of an exemplary stereotactic guidance system 100 (e.g. Medtronic Nexdrive Micropositioning Drive attached to the Medtronic Nexframe®) mounted to a patient's skull. FIG. 1A illustrates a ring 120 of guidance system 100, which extends around a perimeter of a burr hole 11 formed in the skull, supporting a socket assembly 140 to which a micropositioning drive 160 is attached. Burr hole 11 may be fitted with a base ring 112 (FIG. 1B; e.g. the Medtronic Stimloc base) that is mounted around burr hole 11 prior to attaching ring 120 of guidance system 100. FIG. 1 further illustrates an elongate medical device 15, for example, a medical electrical lead carrying one or more stimulating electrodes, held within drive 160 for advancement through burr hole 11 and into the target region of the brain.
FIG. 1B illustrates a portion of the implanted device 15, after guidance system 100 is removed, extending proximally out from base ring 112, which lines burr hole 11, and which is fastened to the skull, for example, via screws received through holes 106 in base ring 112. Those skilled in the art appreciate that a proximal portion of implanted device 15, outside the cranial space, may be routed, beneath the scalp and subcutaneously, to a therapy generator (not shown), for example, implanted in proximity to the clavicle. FIG. 1B further illustrates device 15 extending through a slot of base ring 112 so that device 15 may be secured/anchored between base ring 112 and a cap that snaps into place thereover (not shown; e.g. the Medtronic Stimloc cap). Although various configurations of apparatus for securing elongate medical devices in body portals, such as burr holes, are known in the art, there is still a need for new and improved anchoring apparatus and methods, for example, to increase the ease by which anchoring is activated, without dislodging the implanted device, and without compromising the stability of anchoring.